It is desirable in motor vehicles to provide a sun visor which slides adjacent the windshield or side window to provide different areas of effective sun blocking protection. Such slidable sun visors must minimize the slide effort of the visor, while still controlling lateral play and flutter during operation of the vehicle. Unfortunately, the tighter the design fit between mating surfaces of the visor assembly, the greater the slide effort typically must be. U.S. Pat. No. 5,161,850, for example, shows a visor assembly in which a visor body is laterally adjustable along a slide bar. The slide bar and the visor body each have a frictional engagement member for providing a frictional engagement force between each other. The frictional forces provided by both of the frictional engagement members, however, cannot be selectively applied and released, but rather are constant. As a result, the set, relatively high frictional forces must be overcome in order to slide the visor body along the slide bar. U.S. Pat. No. 5,409,285 shows another visor assembly in which the sliding frictional force cannot be selectively applied and released. Furthermore, as the tolerance fit between component parts increases from continued use, the amount of lateral play and flutter will likewise increase.